Islam, according to its believers, was founded by the prophet Muhammed after the angel Gabriel recited to Muhammed the Quran. However, preaching early on caused a lot of hostility with Meccan tribes. He and his followers attempted to flee to Medina in 622 AD. However, hostile Meccan tribes murdered Muhammed in 622. His followers in Medina regrouped and, after nine years of warfare, in a nearly uncontested battle, took Mecca and destroyed its pagan idols. By 634 AD, the Arab peninsula was unified under Islam. However, the Ummah was split over who should become the caliph of Islam. The people who believed that Abu Talib should become caliph became known as Talibids and the people who believed Abu Bakr should become caliph became known as Bakrites. For ten years, a devastating civil war raged in Arabia until Abu Bakr became leader of the Islamic Caliphate and the first of the Bakrite Dynasty. The weakened caliphate was unable to launch successful invasions in both the ruins of the Sassanid Empire and the Byzantine Empire.